1. Field of the Invention
This invention relates generally to breakaway pipe couplings for insertion in a marine hose or pipeline. More particularly, this invention relates to breakaway pipe couplings designed to separate in a controlled manner under tensile loads exceeding a predetermined limit so that the hose or pipeline into which the coupling is connected will be protected against permanent structural damage.
2. Description of Relevant Art
Breakaway pipe couplings for use in pipelines for transmitting oil and other liquid fuels or fluids are known; one commercially available breakaway pipe coupling is described in U.S. Pat. No. 4,059,288, granted Nov. 22, 1977, to Harvey O. Mohr. Another commercially available breakaway pipe coupling is described in European Patent Application Publication No. 6278A1, by Gall Thompson published Jan. 9, 1980.
The Mohr patent discloses a separable safety pipeline connector which will yield at a predetermined tension. The connector of this device includes a housing having one axial end adapted for connection to the pipeline, with the other axial end open. The connector includes a pipe extension member having one axial end adapted for connection to the pipeline for transmission of line fluids therethrough, and the other axial end arranged to telescopically fit in the connector housing in a sealed relationship. A shear disc is mounted between the housing and extension member for restraining the same against axial separation in response to axial tension forces applied thereto. The shear disc ruptures at a predetermined level, so that axial separation is prevented below such level and axial separation is permitted above such level.
The pressure balanced, breakaway pipe coupling disclosed by both the aforementioned Mohr patent and Thompson application, while recognizing a definite need in liquid fuel pipeline technology, suffer several structural and functional shortcomings. For example, both couplings allow instantaneous separation without regard for the rate or magnitude of the applied load. Thus, even a momentary tension overload will cause complete separation of the pipeline and massive spillage of the fluid within the pipeline. In addition, in the Mohr coupling, no means are provided for terminating the fluid flow through the coupling by sealing the ends of the pipe segments. Thus, the contents of the pipeline can be discharged into the environment. Furthermore, this coupling design is expensive to manufacture and install.
Additional relevant U.S. art includes U.S. Pat. Nos. 427,305; 893,911; 1,162,117; 1,526,218; 2,300,483; 2,948,553; 2,991,090; 3,520,331; and 3,921,656.